Internal combustion engines are any of a group of devices in which the reactant of combustion, e.g., oxidizer and fuel, and the products of combustion serve as the working fluids of the engine. Internal combustion (IC) engines can be categorized into spark ignition (SI) and compression ignition (CI) categories. SI engines, i.e. typical gasoline engines, use a spark to ignite the air-fuel mixture, while the heat of compression ignites the air-fuel mixture in CI engines, i.e., typically diesel engines. The basic concept of the design of both a typical gasoline engine and a diesel engine has not changed for more than 100 years.
The basic components of an internal combustion engine are well known in the art and include the engine block, cylinders, pistons, valve, crankshaft and camshaft. Such an engine gains its energy from the heat released during the combustion of the non-reacted working fluids, e.g., the oxidizer-fuel mixture. In all internal combustion engines, useful work is generated from the hot, gaseous products of combustion acting directly on moving surfaces of the engine, such as the top or crown of a piston.
One of the primary and consistent design goals for internal combustion engines is to increase power and torque. Until very recently, simple upward scaling of the size and/or capacity of the engine and associated components was a feasible way, and perhaps the easiest way, to achieve this goal. That is, horsepower and torque could be increased simply by increasing piston displacement, air flow capacity, etc. Piston displacement is directly dependant on the size of a crankshaft. The earliest evidence of a crank-connecting rod system as a part of a machine is traced back to 3rd century AD. The crankshaft contains two or more centrally located coaxial cylindrical or “main” journals and one or more offset cylindrical crankpin or “rod” journals. The crankshaft main journals rotate in a set of supporting main bearings, causing the offset rod journals or “throw” to rotate in a circular path around the main journal centers, the diameter of which is twice the offset of the rod journals. In the engine having a piston reciprocally disposed in a cylinder extending through the engine cylinder block, the piston is normally connected to a rotating crankshaft by means of a connecting rod. One end of this connecting rod is connected to a wrist pin disposed inside of the piston and accordingly, reciprocates along a straight line. The other end of the rod is journaled on the throw projecting from the crankshaft and accordingly, travels in the circular path. The diameter of that circular path is equal to the distance the piston moves up and down or “piston displacement” in its cylinder, which is called a “stroke”. In a typical arrangement of an internal combustion engine a piston cylinder centerline intersects the longitudinal axis of the crankshaft. If the crankshaft is configured appropriately, the engine may benefit through increased torque placed on the crankshaft as well as a reduction in friction forces between the piston and the piston cylinder.
Referring to FIG. 1, an alternative to the above-described conventional crankshaft is a crankshaft-free driveshaft and piston assembly. This apparatus is disclosed generally in pending U.S. patent application Ser. No. 12/151,954 to Michael Inden, filed on May 12, 2008, titled Crankshaft-Free Drive Shaft and Piston Assembly of a Split-Cycle Four-Stroke Engine, which is herein incorporated by reference in its entirety. The apparatus 20 (for simplicity of the drawing and description the cylinder block of an engine and other engine components are not shown) is a driveshaft and piston assembly that comprises a rotary driveshaft 22 (hereinafter referred to merely as “a shaft”) of a square cross-section which includes a circular eccentric 24 mounted in its indexed position and a pair of integrally mounted cylindrical bushings 26a and 26b. The shaft 22 is journaled at the bushings 26a and 26b for rotation about a shaft axis 28. A connecting rod 30 is pivotally connected to both the circular eccentric 24 of the shaft 22 and a piston 32 at its top distal end. The mechanical linkage of the connecting rod 30 to the piston 32 and the circular eccentric 24 which is indexed on the shaft 22 serves to convert the reciprocating motion of the piston (as indicated by directional arrow A for the piston 32) to the rotational motion (as indicated by directional arrow B) of the shaft 22. The cylindrical bushings 26a and 26b have a coaxial opening of substantially the same cross-section as a cross-section of the shaft 22 of FIG. 1.
Though this embodiment of the invention shows cross-sections of the shaft 22 and the opening of the circular eccentric 24 as substantially square, it is within the scope of this invention that other cross-sections may also be employed, such as other polygons with different numbers of sides, ellipses, or others which will assure an indexed position of the circular eccentric 24 on the shaft 22.
FIGS. 2 and 3, which are schematic diagrams of an exemplary embodiment of two circular eccentrics 36 and 38, illustrate how orientation of openings 40 and 42 for mounting circular eccentrics on a shaft provides indexing of the circular eccentrics on the shaft. FIG. 2 illustrates the circular eccentric 36 which has an opening 40 of substantially the same cross-section as a cross-section of the shaft 22, positioned at a distance E from the center of the circular disk 36. The opening 42, of the substantially same cross-section positioned at the same distance E from the center of the circular disk 38 in FIG. 3, is turned at an angle G, with respect to the position of the opening 40 of the circular eccentric 36 of FIG. 2. Because in a four-stroke cycle engine, a four stroke cycle is completed in two revolutions of a shaft, the second index angle is equal to 720 degrees divided by the number of pistons in an engine and so on. Because in a two-stroke cycle diesel engine, a stroke cycle is completed during one revolution of a shaft, the second indexed angle is equal to 360 degrees divided by the number of pistons in an engine.
Many attempts have been made over the years to increase the efficiency of the conventional engine design. Because the internal combustion engine works partially off of the torque created by the rotation of the crankshaft, it is important that the engine creates as much torque with as little effort in order to be more efficient and use less fuel in the process. One such attempt involves laterally offsetting the axis of rotation of the crankshaft from the axis of the piston cylinder.
With different reasoning, but with the same goal to improve torque and power of the engine, several technologies relating to reciprocating piston mechanism in which the crankshaft axis is offset from the piston cylinder axes have been proposed in U.S. Pat. Nos. 810,347; 2,957,455; 2,974,542; 4,628,876; 4,708,096; 4,945,866; 4,974,554; 5,070,220; 5,146,884; 5,186,127; 5,544,627; 5,749,262; 5,816,201; 6,058,901; 6,202,622 and 6,460,505; in Germany patent documents 2,855,667 and 3,410,548; Great Britain patent documents 1,133,618 and 2,219,345; in France patent document 2,593,232; Japan patent document 60-256,642. One such attempt involves controlling timing of combustion within the cylinder to cause maximum combustion pressure within the cylinder during a power stroke to occur when the piston cylinder centerline coincides with the respective throw connection axis of the crankshaft. Typically, the offset in this kind of configuration is less than a half of the throw of the crankshaft. In another attempt, the offset crankshaft is located such that at a point during the power stroke the crankshaft throw is perpendicular to the vertical axis of the piston cylinder and the connecting rod is substantially collinear with the vertical axis of the piston cylinder. This configuration leads to a long connecting rod. In yet another attempt, in order to maximize the offset of the cylinder, a curved, bowed-shaped or offset connecting piston rod is added with the intention to increase the engine torque and overall power. Force, moving the piston down the cylinder is transmitted to the crankshaft in the direction from the wrist pin disposed inside of the piston to the offset rod journal of the crankshaft. The other component of the piston force is responsible for friction loses between the piston and the cylinder. In these particular configurations with the offset connecting rod, increase in the crankshaft rotating force is negated by significantly increased friction loses between the piston and the cylinder.
Thus, none of the above mentioned approaches which involves laterally offsetting of the axis of rotation of the crankshaft from the axis of the piston cylinder, allows any significant improvement of the torque created by the rotation of the crankshaft and consequently engine power and efficiency without significant enlargement of the crankshaft.
Output power of an engine is defined as a product of torque, speed of rotation of a shaft and units' conversion coefficient. The magnitude of the torque depends on a force applied and a moment arm, which is a distance from the axis of rotation to the direction of the force application. In cases involving an internal combustion engine with a crankshaft, the offset rod journal, or throw of the crankshaft, rotates in a circular path around the main journal center and moves the bottom distal end of the connecting rod from one side of the centerline of the cylinder to another. Thus, during a power stroke when combustion is taking place in the combustion chamber of the cylinder, the length of the moment arm fluctuates from 0 to the length of the crankshaft throw and back to 0. All of this leaves little room for an engineer to influence the output power.
Accordingly, there is still a need to increase the torque generated during a power stroke of an internal combustion engine, and thus, increase power output of the engine or decrease fuel consumption for desired power output of the engine and increase engine efficiency and the present invention resolves this need by providing a mechanism to increase the force applied to the driveshaft moment arm.